8 replies to this topic

[pablohoney]

I am searching for a cable tension measuring device for a structural application.
I was wondering what type of tool is used to measure the tension in a lift cable?
Are there special companies that measure the tension periodically?
thanks
pablo

[liftmech]

If I'm understanding you correctly, you're looking for a tool that is attached to the centre of the cable and pulled until the cable reaches a certain deflection; the tension is then read off a digital or analog scale. We don't use those in the industry; rather, our tension is constant because the counterweighting force is constant. It is calculated before the lift is even built, and then a concrete counterweight is poured or a hydraulic system is built to that specification. The counterweight or hydraulic ram is attached to a movable carriage, which ensures that the tension remains constant.

[pablohoney]

liftmech, on Apr 19 2005, 03:02 AM, said:

If I'm understanding you correctly, you're looking for a tool that is attached to the centre of the cable and pulled until the cable reaches a certain deflection; the tension is then read off a digital or analog scale. We don't use those in the industry; rather, our tension is constant because the counterweighting force is constant. It is calculated before the lift is even built, and then a concrete counterweight is poured or a hydraulic system is built to that specification. The counterweight or hydraulic ram is attached to a movable carriage, which ensures that the tension remains constant.
<{POST_SNAPBACK}>

What I really need is a tool that measures tension in an cable already installed. Doesn't the lift cable stretch over time and require retensioning or replacement?
There is a limit to how much a cable can stretch before breaking.
still curious

[Shawn]

pablohoney, on Apr 19 2005, 04:32 AM, said:

What I really need is a tool that measures tension in an cable already installed.  Doesn't the lift cable stretch over time and require retensioning or replacement?
There is a limit to how much a cable can stretch before breaking.
still curious
<{POST_SNAPBACK}>

Do have any as-built plans for this lift? What type of tension do you have(counterweight or hydraulic0 ?.

[Allan]

The haul rope will stretch over time, and I believe there is a measurement you can do on the length of the lay to see if it's over spec (or is measure the diameter of the rope?). If it is over spec, then yes replacement is in order, as for retensioning - the carriage will take care of that, unless of course the carriage has hit its stops. Maybe you mean resplice? A resplice is if the rope has stretched, but not enough to require replacement.

[liftmech]

Pablo- when you say structural application, are you referring to cables used in buildings to keep the steel frame square?

[pablohoney]

It is a 1/4" dia cable 30' long which ties the bottom of a large together.
The cable is subject to wind, snow, and dead loads and it has been in
service for 20 years. The tension range that I am looking for is from 1000 to 5,000 pounds.
thanks

[coskibum]

you should hire an engineer...they deal with stuff like that :)

[mmsa]

A dynometer would measure the tension of a wire rope. They come in all sizes just a few pounds to well over 50 tons.